Conventionally, the image forming apparatus in which an electrostatic latent image formed on a photosensitive drum is developed into a toner image by using a liquid developer containing a toner and a carrier liquid, and the toner image developed from the electrostatic latent image is primary-transferred onto an intermediary transfer member and further, the toner image transferred on the intermediary transfer member is secondary-transferred onto a recording material has been known. In such an image forming apparatus, a liquid layer of the carrier liquid is formed on the photosensitive drum or the intermediary transfer member, so that the toner image is capable of being developed and transferred.
However, in the case of an excessive carrier in which a liquid amount of the carrier liquid, i.e., a carrier liquid layer is more than a proper amount, improper fixing is liable to occur when the toner image is fixed on the recording material. Therefore, conventionally, an image forming apparatus in which an excessive carrier liquid is removed from the carrier liquid layer has been proposed (Japanese Laid-Open Patent Application (JP-A) 2003-91161). In the apparatus described in JP-A 2003-91161, the excessive carrier liquid is removed from the carrier liquid layer by a sweep roller rotating in contact with the photosensitive drum. However, in this case, when a shortage of the carrier such that the liquid amount of the carrier liquid layer is less than the proper amount occurs, improper transfer occurs due to the shortage of the carrier during transfer of the toner image, and therefore, the liquid amount of the carrier liquid layer after the removal is adjusted to the proper amount.
Further, although an image forming apparatus uses a dry developer, not the liquid developer, an image forming apparatus of a tandem type and an intermediary transfer type in which a plurality of photosensitive drums are juxtaposed in a movement direction of an intermediary transfer belt has been conventionally proposed (JP-A 2010-66452). In this image forming apparatus, as an image forming mode, for example, a full-color mode in which images are formed with toners of yellow, magenta, cyan and black and a monochromatic mode in which an image is formed with only toner of black are selectively executable. Further, during full-color mode, all the photosensitive drums are contacted to an intermediary transfer belt (hereinafter, simply referred also to as a belt), and during monochromatic mode, only the photosensitive drum for black is contacted to the belt.